Computers use disc drives for storing information. Disk drives typically include a magnetic disc that rotates while one or more heads read and write information from and to the disc. Functions of a disc drive usually include a controller for interfacing the drive with the rest of the computer system; a channel function that communicates with the controller, and manages read and write functions of the disc; and a buffer function that acts as a cache for the disc drive, such as an SDRAM (Synchronous Dynamic Random Access Memory). Such devices are typically fabricated using semiconductor processing technology to create integrated circuits having the necessary components to perform the necessary functions.
Traditionally, these disc drive functions are provided in computer systems using multiple packages per disc drive function. For example, buffer functions provided by SDRAM devices are usually provided on one die while controller and channel functions are provided for on a separate die. In current computer systems, these two dies are packaged separately and placed separately on a printed circuit board (PCB).
There are several problems associated with mounting individual chips on a PCB. A chip package is several times the area of the die itself, taking up more space on the circuit board. Circuit resistance is increased by the individual resistances of all the package pins and the electrical path lengths are multiplied by the number of chips and package leads. In current designs, the length traveled by the point-to-point signals and the number of interconnects required between these separate packages have enormous performance and system level implications, such as increased noise, and an increase in required signal strength due to the number of interconnects separating the relevant devices.
Another issue involves the reliability of the ICs (Integrated Circuits) placed on a PCB. In individual package processes, a final test assures the quality of the completed product. If the chip is bad or the process faulty, the entire chip and package is discarded. But when packaging devices together, failure of one of the packaged dies means both must be discarded, adding to waste and increasing the overall cost because of lost good components shared in the package with bad components and the need to increase testing to prevent such loss.
One option is to rely on the results of a wafer-sort test to certify die performance. Unfortunately, wafer sort does not include environmental tests or long term reliability tests. Therefore, there is a need in the art for a reliable alternative to the multi-package solution for disc drive functions.
The present invention provides a solution to this and other problems, and offers other advantages over previous solutions.